1. Field of the Invention
The present invention relates generally to a system and method for analyzing the printing properties of a substrate, and more particularly, to a system and method for analyzing a test pattern printed by a printing device to determine the printing properties of a substrate.
2. Background of the Related Art
The evaluation of the printing properties of a substrate, for example, a paper sheet, traditionally has involved the manual evaluation of printed images on a substrate by highly trained technicians. Due to human involvement, manual evaluation techniques tend to be quite subjective, thus causing a lack of consistency between any two or more evaluations of the same printed image. This is true whether the evaluation is performed by one or more technicians. In addition, the process of manually evaluating printed images is time consuming and, consequently, expensive.
In an attempt to eliminate the subjectivity inherent in manually evaluating printing properties of a substrate, a number of standard test patterns have been developed. The test patterns are typically designed to magnify expected paper deficiencies. The test patterns are advantageous because they eliminate the need for a technician to rely solely on the printed image in his evaluation. For example, if a well known Graphic Arts Technical Foundation (GATF) dot-growth test pattern is printed on a substrate and a predetermined amount growth occurs, portions of the test pattern visibly merge. Wile the standard test patterns have improved the evaluation of printing properties of a substrate to a limited extent, some subjectivity still remains and, therefore, the results remain prone to error.
More recently, computer-based print analysis systems have been developed. The computer-based systems have eliminated a number of problems associated with the manual evaluation techniques. In particular, because the computer-based systems operate automatically according to software instructions, the subjective nature of the manual evaluation techniques has been virtually eliminated. In addition, the amount of time in which it takes to evaluate printing properties has been substantially reduced.
One such print analysis system available for evaluating the printing properties of a substrate is ImageXpert(trademark) (KDY Inc., Nashua, N.H.). ImageXpert(trademark) applies algorithms embodied in print analysis software to evaluate test patterns in order to quantitatively measure the printing properties of a substrate. The software carries out a number of tests on standard test patterns, including assessing dot quality, line quality, edge sharpness, and feature resolution. Although automated systems such as ImageXpert(trademark) have improved results obtained in evaluating the printing properties of substrates, there are several problems with these prior art computer-based systems.
For example, existing printing property analysis systems evaluate the test patterns in a one-dimensional manner. More specifically, these prior art systems typically evaluate only overall growth of a test pattern printed on a substrate. Importantly, however, the systems do not consider multi-dimensional growth of a printed test pattern. More specifically, existing print analysis systems do not consider: (i) the change of a test pattern""s area through wicking of ink into the substrate; and (ii) the change of a test pattern""s area through bleed occurring between contiguously printed inks. Accordingly, these prior art print analysis systems tend to overlook certain important defects due to multi-dimensional growth.
Also, because test patterns must be scanned into a computer which supports print analysis software, errors may be introduced into the test patterns due to the rectilinear geometry of most standard test patterns in use. That is, misalignment of the straight line edges of standard test patterns with the scanner heads of scanners tend to introduce aliasing errors that affect the results.
The above problems may be exacerbated by the fact that the printed test patterns are often printed on printers driven by printer drivers which introduce additional variables not accounted for in print analysis software, Thus, the data that is analyzed by the print analysis software may not be an accurate representation of the original test patterns.
In view of the above, there is clearly a need in the art for an improved method and system for evaluating the print quality of a printing device which solves the foregoing problems.
The subject invention is directed to a novel and unique system and method for print analysis. The system and method is used for analyzing a test pattern printed by a printing device onto a substrate to determine the printing properties of the substrate.
A system is disclosed for determining print defects of a test pattern formed on a substrate by a printing device, the system includes a memory storing a first digital representation of the test pattern, wherein the test pattern comprises (i) a first cell having a background of a first color and a pattern of a second color and (ii) a second cell having a background of the second color and a pattern of the first color. The system further includes a processor in communication with the memory, the printing device, and a scanner. The processor is programmed to print the test pattern onto the substrate using the printing device, receive from the scanner a second digital representation of the test pattern, and analyze at least a portion of the second digital representation of the test pattern to determine the print defects of the test pattern.
A method is disclosed for determining print defects of a test pattern formed on a substrate by a printing device, the method includes generating a first cell of the test pattern on the substrate, wherein the first cell has a background of a first color and a pattern of a second color, generating a second cell of the test pattern on the substrate, wherein the second cell has a background of the second color and a pattern of the first color, converting the first and second cells into a digital representation of the test pattern, and analyzing at least a portion of the digital representation of the first and second cells to determine the print defects of the test pattern.
The patterns of the first and second colors each have a plurality of dots. In addition, each of the plurality of the dots has a diameter of 0.1 inch. Further, each dot of the pattern of the first color has a unique x and y coordinate and each dot of the pattern of the second color has unique x and y coordinates that correspond to a dot of the pattern of the first color.
The analysis described above can include determining a first mean area of the pattern of the first color, determining a second mean area of the pattern of the second color and evaluating a difference between the first and second mean areas to calculate a gain index of the test pattern. Alternatively, the analysis can include determining a first amount of migration between the pattern of the second color and background of the first color, determining a second amount of migration between the pattern of the first color and the background of the second color, and evaluating a difference between the first and second amounts of migration.
The method can further include generating a third cell of the test pattern on the substrate, wherein the third cell has a background of the first color and a pattern of the first color. In addition, generating a fourth cell of the test pattern on the substrate, wherein the fourth cell has a background of a second color and a pattern of a second color.
The analysis can then include selecting a color-band for the first and second colors, determining a first amount of the first color in the first and second cells from the selected color-band, determining a second amount of the second color in the first and second cells from the selected color-band, determining a third amount of the first color in the third and fourth cells from the selected color-band, determining a fourth amount of the second color in the third and fourth cells from the selected color-band, and determining a non-uniformity index based on a ratio of a difference between the first and second amounts to a difference between the third and fourth amounts.
A raggedness index can also be calculated by first determining a mean circularity of the dots of at least one of the patterns. The raggedness index is then determined by dividing the mean circularity by a predetermined value.
Another method is disclosed for assessing the print quality of a printing device. The method includes printing a test pattern onto a substrate using the printing device, wherein the test pattern comprises (i) a first cell having a background of a first color and a pattern of a second color and (ii) a second cell having a background of the second color and a pattern of the first color. The substrate having the test pattern printed thereon is scanned to generate a digital representation of the test pattern. At least a portion the digital representation of the test pattern is then analyzed to determine the print quality of the printing device.
Further features of the system and method for print analysis will become more readily apparent from the following detailed description taken in conjunction with the drawings.